EHX - Clockworks EH5385  [schematic]

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JuliaDee
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Post by JuliaDee »

Hello FreeStompers. I recently unearthed a file folder of Clockworks documentation and am pleased to be able to publish the info here for your entertainment. From the file notes it looks like I had the original concept idea in 1977, but didn't get around to actually building anything until late 1980. My first attempt apparently involved non-retriggerable one-shots but that was less than satisfactory and was abandoned in favor of the analog frequency divider approach that ultimately went into the product.

I've designed literally hundreds of products that have gone into production over the past 35 years, but I think this may be the one of which I'm most proud, both for what it does and how it does it.

I'm attaching both the (redrawn, as my originals were a bit marked up and confusing) schematic and a scan of the original instruction booklet. I also have a somewhat ratty photocopy of the (single-sided) PCB layout if anyone's interested.

One aspect of the rig that can be viewed as either a drawback or a feature is that being entirely analog, you can't save your settings. And believe me, the permutations are so vast that you'll never get the same thing twice, so keep your recording equipment running. In a way, this makes it a more "pure" performance instrument, but at times you really will wish you could save a particularly awesome patch. It's long been a fantasy of mine to realize the whole system in the digital domain, but time has never permitted. I did spend a month or so during a dry spell about three years ago trying to implement it in desktop software, but the SDK I was using wasn't good at real-time timekeeping. I think maybe a dedicated embedded solution for self-containedness as a performance instrument, with remote desktop configuration and patch management via USB might be the hot ticket.

There's lots of room for UI improvement of course. I was constrained by the E-H sheet metal box and the 10 sliders inherited from the original Graphic EQ, and they are surprisingly playable, but with a free palette of touch controls, gesture sensing etc. you could certainly make it much cooler.

I'll be happy to answer any questions anyone might have.

Thanks to fsb member inlifeindeath for motivating me to get this documentation together.

julia
Clockworks Schematic.jpg
Clockworks Schematic.pdf
EH5385 Clockworks Schematic
(73.97 KiB) Downloaded 1002 times
Attachments
Clockworks Instructions (original booklet).pdf
EH5385 Clockworks Instruction Booklet
(660.48 KiB) Downloaded 656 times

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RnFR
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Post by RnFR »

very cool! thanks a lot, Julia. we at fsb are honored by this look into the past. you definitely don't get to see something like this every day!

edit- the PDF appears to be blank? are you sure it was properly uploaded?
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Post by Scruffie »

Wow :shock: This is amazing! Thank you so much Julia.

I'd certainly love to see the PCB layout you have aswell, I always wondered, did EHX outsource its PCB designs or were they done by the designers themselves? They're all so amazingly symmetrical and well laid out.

Thank you again for providing this information, hopefully some revived units and interest will come of it!

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Post by Scruffie »

RnFR wrote:very cool! thanks a lot, Julia. we at fsb are honored by this look into the past. you definitely don't get to see something like this every day!

edit- the PDF appears to be blank? are you sure it was properly uploaded?
PDFs loaded fine for me.

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Post by Greenmachine »

Thanks Julia!
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Post by JuliaDee »

OK, I'll scan the PCB layout asap. We had an in-house PCB layout guy at E-H, a wonderful man named Harry Fliegelman. I think the designers sometimes grabbed tape and mylar themselves if Harry was overloaded.

julia
Scruffie wrote:Wow :shock: This is amazing! Thank you so much Julia.

I'd certainly love to see the PCB layout you have aswell, I always wondered, did EHX outsource its PCB designs or were they done by the designers themselves? They're all so amazingly symmetrical and well laid out.

Thank you again for providing this information, hopefully some revived units and interest will come of it!

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Post by JuliaDee »

Oops, I meant to attach a photo of the gizmo as well, for those who've never seen one...
Electro-Harmonix Clockworks
Electro-Harmonix Clockworks

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Post by roseblood11 »

...what about those who´ve never listened to one? :D

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Post by JuliaDee »

roseblood11 wrote:...what about those who´ve never listened to one? :D
Um... I've got some stuff on 4-track reel-to-reel but sold my deck years ago, lol.

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Post by Scruffie »

roseblood11 wrote:...what about those who´ve never listened to one? :D
They go to youtube :) about the only demo about for it... sadly not all that wonderful.

It's not something you really listen to though, it's a trigger you'd use with the other EHX Synth/Drum Products from what I gather.

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Post by JuliaDee »

Scruffie wrote:
roseblood11 wrote:...what about those who´ve never listened to one? :D
They go to youtube :) about the only demo about for it... sadly not all that wonderful.

It's not something you really listen to though, it's a trigger you'd use with the other EHX Synth/Drum Products from what I gather.
Yeah, not a great demo on YouTube. You're correct - it has no audio output, just triggers. It was designed at the time for the other E-H percussion devices as you surmise, but it should work with just about anything that has a trigger input.

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Post by Hides-His-Eyes »

You did all that with OPAMPS?

:block: Now I can see why you're so proud of it!

I assume LM324 would be a good op-amp alternative; this seems like the perfect thing to develop as a three-board setup so you can have 2,4,6... channels depending on what case you can get hold of...

Is the op-amp setup doing things that might be done with 4000 CMOS these days, or does the op-amp setup allow the permutation subtlety?

I need some triggerable drum circuits, I think a drum machine with this as a core might be my summer project :)
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Post by JuliaDee »

Hides-His-Eyes wrote:You did all that with OPAMPS?

:block: Now I can see why you're so proud of it!

I assume LM324 would be a good op-amp alternative; this seems like the perfect thing to develop as a three-board setup so you can have 2,4,6... channels depending on what case you can get hold of...

Is the op-amp setup doing things that might be done with 4000 CMOS these days, or does the op-amp setup allow the permutation subtlety?

I need some triggerable drum circuits, I think a drum machine with this as a core might be my summer project :)
The LM339's are quad comparators, not op-amps per se. It also comes in duals and singles; I forget the numbers right now. They have open-collector outputs, which are necessary for resetting the charge pump cap without using an additional transistor, and being comparators they're optimized for fast switching. The LM324 would probably not work nearly as well (lousy slew rate) and would require an external transistor for discharging the 5UF charge pump cap. LM339's are common and cheap.

Although it is possible to make analog comparators with 4000 series CMOS it probably wouldn't work as well as real comparators and would not be worth the bother. Or maybe you meant using 4000 CMOS in a digital approach - well that'd be a whole different kettle of fish. If you're going digital you'd be much better off using a microcontroller imo. And yes, a lot of the Clockworks' magic comes from its analog-ness - you can get the divisors on the hairy edge where they sometimes divide by one number and other times by the number just adjacent to it. There's probably crosstalk and other analog "imperfections" that contribute to its organic-ness. You could conceivably simulate this randomness in a digital implementation as well, but it'd be a big project. The best place to start might be building the original (which should take only an hour or so on a protoboard) to get a feel for what it does and then decide where you want to go from there.

I hope you do build it, and good luck!

julia

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Post by Hides-His-Eyes »

There's a guy here in the UK who makes a 'tap-tempo' LFO IC that would offer a square signal at 1-4x a frequency made by closing a switch; I think that might be a good way to bring the design into the 21st century while still keeping the quirkiness of the dividers. I'll stick some comparators in my next order and give it a go with that. :)
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Post by Hides-His-Eyes »

Do you think it would run on 9V? Depending on what I can find for drum circuits I might have to use a charge pump already for making a bipolar supply (when synth circuits are written for +-15, I always figure it's not worth converting to virtual ground if that would only leave the circuit with +-4.5V!) and I wouldn't want two of the things heterodyning.
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Post by JuliaDee »

Hides-His-Eyes wrote:Do you think it would run on 9V? Depending on what I can find for drum circuits I might have to use a charge pump already for making a bipolar supply (when synth circuits are written for +-15, I always figure it's not worth converting to virtual ground if that would only leave the circuit with +-4.5V!) and I wouldn't want two of the things heterodyning.
You could try it on 9V; there will just be that much less error/noise margin for the frequency dividers. The staircase steps in the dividers are about 1/15 of the supply voltage (1UF÷15UF), so at 9V they'd only be about 600mV each. Capacitor droop on the staircase steps on the 15UF caps could become an issue, as might the 741's output swing.

I think it takes a fair amount of current since it's constantly pumping those four 1UF caps (and the LEDs) so a charge-pump based power supply may not be the best approach. Better to make a real ±15V supply and then regulate down from that with linear or switching regulators if you have stuff that absolutely must run at lower voltages.

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Post by Hides-His-Eyes »

Could you use a 10uF there instead and use a smaller trimmer accordingly to still get the 8 steps? 15u 10% is not a common value; mouser have it but otherwise I'd have to stack a 10 and a 4.7. Not the end of the world but if the 10u might work better with the 9V supply it might be worth it.
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Post by JuliaDee »

Hides-His-Eyes wrote:Could you use a 10uF there instead and use a smaller trimmer accordingly to still get the 8 steps? 15u 10% is not a common value; mouser have it but otherwise I'd have to stack a 10 and a 4.7. Not the end of the world but if the 10u might work better with the 9V supply it might be worth it.
The staircase step size = clock voltage * input cap / storage cap. So with the original values you have
  • ≈15V clock swing * 1UF/15UF = 1V per step.
The tradeoffs are:
  • A smaller step makes everything more critical - noise, crosstalk, cap leakage, trimmer sensitivity, etc. You want the steps as large as possible while still being able to achieve the maximum desired divisor, i.e. 8.
    A bigger input cap means more load on the clock and more supply current.
    A smaller storage cap means more sensitivity to leakage currents.
I'm sure there's room to play around with the values some, you'll just have to fiddle with it. That's what protoboards are for :-)

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Post by e45tg4t3 »

Hi There Guys and Girls,
At the moment i´m trying to route a layout for the Clockworks, but came across a little strange piece in the schematic... so are the connections from the base´s of the two power transistors(2n6111/2n6290) to the Supply Pins of the 741 correct? Just seems a little strange to my eyes...

Best Regards

Ben

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Post by JuliaDee »

Yes, the schematic I posted here is correct. For another example of this type of op-amp output booster see Walt Jung's IC Op-Amp Cookbook fig 6-25. It's on page 311 of my 1976 edition...

Julia
e45tg4t3 wrote:Hi There Guys and Girls,
At the moment i´m trying to route a layout for the Clockworks, but came across a little strange piece in the schematic... so are the connections from the base´s of the two power transistors(2n6111/2n6290) to the Supply Pins of the 741 correct? Just seems a little strange to my eyes...

Best Regards

Ben

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